Although this year's Cannes selection contained many of the world's most fashionable auteurs, politics and real life remained dominant themes as the festival drew to a close. It was not, therefore, a surprise that many wanted Michael Moore to carry off the Palme d'Or.

Moore, hardly the most stylish man on the Riviera, rolled into town with his Farenheit 9/11 and certainly caused the most fuss. The film is provocative, funny and moving but it is also unfocused, ranting and one-sided. It is the J'Accuse de nos jours, with Moore as the impassioned Zola - never the most elegant essayist but always one of the loudest and most popular - and it might just have the power to change the world by losing George Bush the next election.

Moore paints Bush as a clown, a president who spends more time playing golf (badly) than he does running the country (also badly). More damagingly, he proves the Bush family's business links with the bin Laden family and, by the end, has blamed their nepotistic dynasty for most of the world's evils.

The first half thrives on Hogarthian satire, taking a jocular tone detailing what he sees as unbelievable chicanery among the most powerful men in the world. 'Was it all a dream?' breathes Moore, revealing the brazen abuse that won the Florida election, the media's role in creating national panic and the US army's shameful recruitment policies. All of these topics meet the withering Moore sarcasm - Bush and his father are seen repeatedly shaking hands with Saudi Arabian princes to REM's 'Shiny Happy People' - and, assembled here as a vast jigsaw of the current political situation, it makes a riveting picture.

Subtlety is about the only thing not on Moore's menu. He does often come across as the pub bore getting progres sively more intoxicated by the sound of his own fury and his screen presence is considerably less charismatic than his voiceover.

It is important, however, to put politics aside for a moment and consider Moore's work in the context of Cannes, which means as a piece of film-making. It isn't the most elegant of documentaries: the later footage of US soldiers in Iraq, torturing prisoners or writhing in amputated agony, is impressive but is more the stuff of TV news. Compared to, say, Errol Morris's The Fog of War, it looks shabby and flabby. What it proves is the currency of the documentary as a quintessentially modern art form, as open to subjectivity, personal vision and authorial voice as any auteur's work. Selecting it for Cannes emphasises the form's ascendancy and (fork)lifts Moore to the top of the pile.

It is not my favourite. Japan's Hirokazu Kore-Eda and his sublime Nobody Knows still holds that position. But it is closely followed by two splendid biopics, The Life and Death of Peter Sellers and The Motorcycle Diaries .

Geoffrey Rush is brilliant as Sellers and will be at least nominated for an Oscar. He nails all of Sellers's iconic roles with aplomb and - much harder - impeccable comic timing. Pinning down Sellers himself is more elusive, but then that's the point Stephen Hopkins's film is making. And it does so with a verve and invention rarely seen in this most treacherous of genres. Beginning in a dank Britain of Goon Shows and Emily Watson (who plays his wife Anne) in a cardie, Hopkins sees Sellers as a bright star illuminating the dull scene, using to-camera confessionals, hallucinatory sequ-ences, reconstructions of famous film scenes (from The Ladykillers to I'm All Right Jack through Dr Strangelove and The Pink Panther to Being There), backstage fights, and Charlize Theron out Eklanding Ekland in the sex kitten stakes. The production design and array of techniques are dazzling and, topped by Rush's tour de force, the film - showing last - came as a final firecracker. The film's daring conviction comes as some surprise.

Stephen Hopkins, a Brit born in Jamaica and now living in America, has hardly hinted at such elan - his filmography includes Nightmare on Elm Street 5, Predator 2 and Lost in Space - but he delivers some of the festival's most memorable coups de cinema. From the Saul Bass-influenced opening credits to the spot-on recreation of Clouseau's spinning globe pratfall and a delirious sequence in which Sellers's characters taunt him on his hospital bed, the film bursts with the sort of artistic creativity the biopic form so often precludes. Even the casting throws up constant surprises: John Lithgow as Blake Edwards, Stephen Fry as a charlatan quack and Nigel Havers as David Niven.

The Motorcycle Diaries finds Brazilian Walter Salles making the most artistically assured film of his career and the best all-round work on show here. Interestingly, it also borrows documentary techniques to film the young Che Guevara's memoir of a 1952 journey through South America with his friend, Alberto Granado. Visually, this is a seductive triumph, bursting with tinted images (shot by Eric Gautier) that capture the landscapes and local people like the pages of an old National Geographic. Gael García Bernal turns in his second fine performance of the festival (after Bad Education opened proceedings) as a young man being shaped by experiences.

After Central Station and Behind the Sun, it's becoming clear that Salles is a director not only of style and intelligence but also - and more importantly - of great heart, concerned with the landscape's effect on his characters. His films don't operate in a cold vacuum of artistic pomposity but resonate with warmth and humanity. Beauty, for Salles, is not something you admire but something you earn.

The same can, unfortunately, no longer be said of Wong Kar Wai. If there was one film I was looking forward to more than any other, it was his 2046 . And how he kept us waiting, still tinkering with the film even as it went up the Palais steps just an hour before its gala screening. It was the biggest disappointment of the festival, and possibly the only dud of his career.

His films (such as Days of Being Wild, Chungking Express, Happy Together and In the Mood for Love especially) are delicately nuanced pieces that build to joyous emotional climaxes, but 2046 is baffling and chilly. It fails to develop its characters, gives them wretched dialogue and misses nearly every beat. It concerns a writer (Tony Leung in Clark Gable mode) and his love affairs (with Zhang Ziyi, Gong Li and Maggie Cheung). Shot in a similar style and locale to In the Mood for Love, the action flits from Hong Kong, 1968, to Singapore and the future where, in a zone called 2046, people escape to recapture their memories, never to return. Various chapter headings spout portentous nonsense such as 'All memories are moist' and 'When the peony blooms she stands straight and tall'. With 2046, this usually brilliant director is not so much recapturing memories as dining out on them.

The other auteurs in competition all contributed interesting films - that's what makes them auteurs, see - but most have done better before. Lucrecia Martel, from Argentina, earned many admirers with her second feature La Niña Santa (The Holy Girl), but I was not among them. The story of a teenager in a rural hotel, her sexy mother and a convention of doctors, was certainly stylish but failed to ignite or convey local atmosphere as successfully as her debut feature, La Ciénaga ( The Swamp ). The Coen brothers returned to Cannes with a remake of The Ladykillers, transposing the action to the Deep South and serving up a slice of southern gothic black comedy suffused with gospel music. The team's writing has customary polish and wit ('Madam, to flog a horse that, if not dead, is in mortal danger of expiring...') but the direction runs out of steam and Tom Hanks's Goldthwait Higginson Dorr is a bizarre creation - Alec Guinness by way of Dick Emery.

Oliver Assayas contributed the most banal film, an arm-chewingly insipid piece called Clean, about a former rock chick's (Maggie Cheung) efforts to kick heroin and regain her son back from his grandfather (Nick Nolte). Tony Gatlif ran him close with Exiles, a road movie about an intensely annoying couple's journey on foot from Paris to Algeria, taking in gypsy communities and lots of flamenco dancers. It slightly redeems itself with an extraordinary final scene featuring a sort of spiritual exorcism, but even the music is not up to the director's usual standards.

Old Boy, a film by Park Chan-Wook, from Korea, split audiences. Many liked its quasi-Jacobean revenge plot and ultra-stylish violence. I understand jury president Quentin Tarantino was impressed - it features a man fending off countless assailants, being strapped in a chair and having his teeth pulled out by pliers and eating a live octopus. I found the whole thing witless and cruel, especially if you're an octopus.

Outside the main competition, in Un certain regard, was the only pure British entry, from Scottish debut director Shona Auerbach. Dear Frankie stars Emily Mortimer (on impressive form) as a single mother pretending to her deaf son, by writing letters, that his dad is away at sea. Auerbach does a fine job photographing the film too, but the script is terribly undernourished, rather like little Frankie who only eats chips.

Dare I say it but, among all the grand works, Bad Santa was one of the most pleasurable. Billy Bob Thornton is a drunken, safe-cracking, chain-smoking, foul-mouthed, sex-crazed, kid-hating, misery-guts Santa Claus who, along with his black elf accomplice, robs shopping malls on Christmas Eve. Terry Zwigoff's film oozes misanthropy and is wonderfully, bitterly funny throughout. It's not A Wonderful Life, but it was a very good Cannes.

Trash d'Or: Jason Solomon's festival awards

Best film Nobody Knows, by Kore-Eda Hirokazu

Best actor Geoffrey Rush (The Life and Death of Peter Sellers)

Best actress Agnes Jaoui (Comme une Image)

Best director Walter Salles (The Motorcycle Diaries)

Best cinematographer Eric Gautier (Motorcycle Diaries and Clean)

Best music The Ladykillers' gospel soundtrack

Sexiest person (tied) Charlize Theron as Britt Ekland in The Life and Death of Peter Sellers and Gael García Bernal as Zahara the drag queen in Bad Education

Angus Deayton award for drug taking The corrupt mayor and his deputy in Emir Kusturica's Life is a Miracle who hang off the front of a slow-moving train snorting lines of cocaine sprinkled along the tracks.

Best party The opening night gala for Bad Education, ferried guests in by boat, featured achingly beautiful fireworks set to the film's music and then a raucous drag show with Javier Camara, Pedro Almodóvar, Victoria Abril and Gael García Bernal. The Ladykillers party provided the best food (gumbo, cornbread and jambalaya) and had diva Jocelyn Brown backed by a 10-strong gospel choir. MTV, in Liz Taylor's old villa in the hills, had the best views and the best DJs - Ross Allen and Patrick Forge played tag upstairs while Grandmaster Flash dropped old skool hip hop in the basement and I dropped cognac shots down my new T-shirt.